First report of Epicoccum latusicollum causing leaf spot disease on red maple (Acer rubrum L.) in China: Insights from a sentinel planting garden

Red maple (Acer rubrum L.), a tree species native to North America, has been introduced and widely cultivated for timber and ornamental purpose in China. In May 2021, black-brown leaf spots were observed on 3-year-old red maple saplings in a sentinel planting garden located in Lishui district, Jiangsu Province, China. This disease reduces not only the growth but also the ornamental value of affected trees. From symptomatic red maple leaves, three fungal isolates were recovered and subjected to pathogenicity tests by inoculating healthy leaves with mycelium plugs. The isolate EL.1 induced leaf disease successfully with symptoms like those observed in the field, and it was subsequently re-isolated from infected leaves. On PDA media, isolate EL.1 produced spherical brown pycnidia, and its colony displayed a transition from white to grayish with reddish-brown diffusible pigments. Ellipsoidal hyaline conidia were observed. The morphological characteristics of this fungus matched those of Epicoccum spp. For accurate identification, partial sequences of the internal transcribed spacer region (ITS), TUB2 and RPB2 genes were amplified and sequenced. Phylogenetic analysis verified the species as Epicoccum latusicollum. This marks the first record of E. latusicollum on red maple and emphasizes the vital role of sentinel gardens in elucidating novel pathogen-plant host relationships.